The invention relates to a refiner for refining fibrous material, the refiner comprising at least one first refining surface and at least one second refining surface, which are arranged at least partly substantially opposite to one another in such a manner that a refiner chamber is formed between them, to which the material to be defibrated is arranged to be fed, and at least either the first refining surface or the second refining surface in the refiner is arranged to move with respect to the opposite refining surface, and at least either the first refining surface or the second refining surface in the refiner comprises blade bars and blade grooves therebetween.
The invention further relates to a method for refining fibrous material, the method comprising refining fibrous material with a refiner which comprises at least one first refining surface and at least one second refining surface, which are arranged at least partly substantially opposite to one another in such a manner that a refiner chamber is formed between them, to which material to be defibrated is fed, and at least either the first refining surface or the second refining surface in the refiner is arranged to move with respect to the opposite refining surface, and at least either the first refining surface or the second refining surface in the refiner comprises blade bars and blade grooves therebetween.
The invention further relates to a refining surface for a refiner intended for refining fibrous material, the refiner comprising at least one first refining surface and at least one second refining surface, which are arranged at least partly substantially opposite to one another in such a manner that a refiner chamber is formed between them, to which the material to be defibrated is arranged to be fed, and at least either the first refining surface or the second refining surface in the refiner is arranged to move with respect to the opposite refining surface, and at least either the first refining surface or the second refining surface in the refiner comprises blade bars and blade grooves therebetween.
The invention further relates to a blade segment for a refiner intended for refining fibrous material, the blade segment comprising a refining surface with blade bars and blade grooves therebetween. Refiners for treating fibrous material typically comprise two, possibly even more refining surfaces substantially opposite to one another, between which there is a refiner chamber to which the fibrous material to be refined is fed. At least one of the refining surfaces is arranged to move with respect to the opposite refining surface. The refining surface may be one integral structure or it may consist of a plurality of refining surface segments arranged adjacent to one another, whereby the refining surfaces of individual refining surface segments form one uniform refining surface. The refining surfaces are typically provided with specific blade bars, i.e. bars, and blade grooves, i.e. grooves, therebetween, fibrous material being refined between the blade bars of the opposite refining surfaces and both the material to be refined and the already refined material being able to move in the blade grooves between the blade bars on the refining surface. On the other hand, the refining surface may comprise protrusions and recesses between the protrusions. The blade bars and blade grooves of the refining surfaces, or the protrusions and recesses of the refining surfaces, may be made of the basic material of the refiner blade or a separate material. The protrusions may also be formed of ceramic grits attached to the refining surface by previously known methods. The refining surfaces, i.e. the blade surfaces, may also be formed of separate lamellae arranged adjacent to or at a distance from one another and fixed to form a refining surface. The refining surface may also comprise a large number of small protrusions and recesses therebetween, in which case the refiner operates by a grinding principle.
The refiner chamber is a space which is formed between the refining surfaces of a stator and a rotor and where the refining takes place. The refining is caused by mutual pressing and motion of the refining surfaces as a result of frictional forces between the refining surfaces and the material to be refined and, on the other hand, due to frictional forces inside the material to be refined. The surface area between the refining surfaces of the rotor and the stator is the refining area, by which the refining between the refining surfaces of the rotor and the stator takes place in the refiner chamber. The shortest distance between the refining surfaces of the rotor and the stator in the region of the refining area is the blade gap.
To increase the production of refiners, it is important to guide the fibrous material to be refined efficiently between the opposite refining surfaces for refining. At the same time, it is naturally important to enable the removal of sufficiently refined material from between the refining surfaces in such a manner that the refined material does not block up the refiner chamber between the refining surfaces and thus weaken the production of the refiner. Particularly in refining surfaces comprising blade bars and blade grooves therebetween, the guiding of fibrous material between the opposite blade bars has been made more effective by providing o special dams on the bottom of the grooves, the dams forcing the material to be refined to move away from the bottom of the grooves to the space between the opposite refining surfaces. However, the effect of the dams is local and does not substantially benefit the whole area of the refining surface. The dams also diminish the hydraulic capacity of the refining surface considerably. Also by changing the height of the blade groove bottom and/or the volume of the blade groove it is possible to try to force the flow of material to be refined to move between the opposite refining surfaces and thus to make the refining more effective. In addition, by tilting the blade bars, it is possible to affect the flow of material to be refined and thus force the material to be refined to pass between the opposite blade bars.
A problem with all these solutions is, however, that they do not significantly improve the guiding of the material to be refined into the refiner chamber without simultaneously weakening the production capacity of the refiner.